Changing the FM and DFM voting mechanics?

The DUP’s latest proposal for the review is to separate voting for the First and Deputy First Ministers. This would mean that in the event of a deal None of his party would have to vote for Sinn Fein. Without such a change even success on the substantive issues could lead to a Mexican stand off on the first day of new business in the Assembly (currently approaching its third year of prorogation).